Dr. Genth's Contributions to Metallurgy. 433 



All the Chinese coins are cast, and are not struck or stamped. 

 Many of those which I have examined showed the impression 

 of the fine sand used for the moulds ; others were hollow, others 

 did not fill the mould completely, or were full of very minute 

 cavities and air-holes; hence the specific gravity was in some 

 found to be considerably smaller than it ought to have been. 



A pupil of mine, Mr. George J. Popplein, of Baltimore, has 

 at my suggestion made in my laboratoiy the following very 

 careful analyses of the various Chinese coins. 



The analytical methods adopted did not materially differ from 

 those generally in use. It was found, however, that tin cannot 

 be accurately determined by dissolving in nitric acid, &c. It \yas 

 therefore always separated in the usual way ; but the binoxide 

 of tin was afterwards decomposed by fusion with sulphur and 

 carbonate of soda, by which method the small quantities of lead, 

 silver, copper, and iron were converted into insoluble sulphides, 

 whilst the bisulphide of tin and sodium was dissolved by water, 

 &c. All the necessary precautions were also taken to ensure a 

 complete separation of the zinc from the copper. The following 

 are the results of Mr. Popplein's analyses : — 



No. 1. Tschen.—Coloxxv, pale brass-yellow, greyish on the 

 fresh fracture; very good cast, with very fine grain, and but 

 very few air-holes inside ; exceedingly brittle. It contains— 



Copper = 63-94 per cent. 



Tin = 3-29 „ 



Lead = 6-03 



Zinc =36-24 



Cobalt = trace 



Iron = I'35 „ 



99-84 



No. 3. Tschen^. — Colour pale bronze-yellow; the composi- 

 tion was not homogeneous ; and with the magnifying glass two 

 alloys, one of a brass-yellow, the other of a pale copper-red co- 

 lour, could be distinguished : the colour of the fresh fracture was 

 greyish ; medium grain, brittle. It contains — 



Copper =60-97 per cent. 



Tin = 0-05 



Lead = 1"56 „ 



Zinc = 35-05 



Iron • = 2-37 „ 



Silver and Cobalt . . . = traces 



100-00 



• II. Onnau (Scheik. Onderz. vol. iv. p. 517 et seq.) has analysed a 

 similar alloy from China, of a copper-red colour. 



